The present invention relates to an optical information recording and reproducing apparatus and an optical disc.
In an information recording and reproducing apparatus for recording and reproducing information on sectors of an optical disc, it is necessary to record information in each sector and reproduce it correctly from such sector. Further, the information recorded must be reproduced without fail. For this purpose, the conventional information recording and reproducing apparatuses confirm the sector address by an address part arranged ahead of the sectors or by counting a sector separation signal inserted between sectors to determine the sector address. Generally, however, the signal generating the sector address is so short in duration that an effective error control is impossible, necessitating a satisfactory guarantee of the reliabilty of the address part. As a corrective action, a system has been suggested (Japanese Patent Application No. 62438/83) in which an address is recorded in a data recording part which is generally more reliable than the sector address part so that when the sector of the address indicated in the directory is to be reproduced at the time of reproduction, the address recorded in the data recording part is referred to thereby preventing the loss of information. This system effectively prevents data from being lost by the non-identification of the sector address.
When the address part is reproduced and compared with the sector address to be recorded in the recording process, however, the address obtained by reproducing the address part of a recorded sector may make up an address of an unrecorded sector by error, in which case data may undesirably be written again in the recorded sector. In such case, the data of the sector thus overwritten is destroyed. In view of this problem of data destruction caused by overwriting or double writing, means of preventing such an overwriting is necessary to improve the data reliability.
With the increase in the recording capacity of the recording medium, on the other hand, a single recording medium tends to be jointly used by a multiplicity of users. Further, the complication of such a method of system operation requires a write protecting means capable of defending each user from other users in those cases where data may be lost by a system operation error, the need for such protection depending on the degree of importance of the data.
Furthermore, if the address part is not reproduced always correctly due to a flaw or drop-out of the recording medium, the address may not be reproduced correctly and may not be read correctly for the difference in environmental conditions or the like at the time of reproduction, although the address may have been reproduced and data recorded correctly in the data recording mode. For improving the data reading reliability, it is not proper to record data in such a sector, and it is necessary to avoid recording data in a sector from which the address cannot be always reproduced correctly.